#include <stdio.h>
#include <time.h>

char get_kth_upper(int k) { // get_kth_upper(1) == 'A'
    return 'A' + k - 1;
}

char get_kth_lower(int k) { // get_kth_upper(1) == 'A'
    return 'A' + k - 1;
}

char get_kth_num(int k) { // get_kth_upper(1) == '0'
    return '0' + k - 1;
}

int main() {

    time_t timep;
    time(&timep);
    struct tm* p = gmtime(&timep);
    int day = p -> tm_mday;
    int month = p -> tm_mon + 1;
    int year = p -> tm_year + 1900;
    printf("%d/%d/%d\n", year, month, day);

    // password: BASE64 + "MTUyMA=="

    char ch = 'y';
    char ch_d = get_kth_upper(day-1);
    char ch_dn = get_kth_num(day);
    char ch_m = get_kth_upper(month-1);
    int year1 = year / 100;
    int year2 = year % 100;
    char ch_y1 = get_kth_upper(year1);
    char ch_y2 = get_kth_upper(year2);

    printf("%c%c%c%c%c%c%c%c (decode this by BASE64)\n", ch_d, ch_y1, ch_y2, ch, ch_d, ch_m, ch_dn, ch_dn);

    return 0;

}